1. Field of the Invention
The invention relates to a method for entering and leaving a film mode, and more particularly, to a method for determining whether to enter or leave the film mode by examining whether a target field is capable of being merged with a neighboring field of the target field, and an apparatus thereof.
2. Description of the Prior Art
In progressive scanning, data of each image is complete, that is to say, data of even rows and odd rows will be played in the same image. Therefore, when using progressive scanning (or double frequency television image techniques) to play an image made up of odd fields or even fields only, the image should be recovered to full frame data so that the image can be presented reasonably. This technique of frame data recovering is called de-interlacing. When de-interlacing an interlaced film data, the neighboring odd field and even field can be combined to form a frame, which will be played twice to meet the requirement of frequency updating.
If the relationship of each field can be detected correctly, the video data mode can be inferred, such as 2:2 pull down or 3:2 pull down. The prior-art techniques determine whether to leave or enter the film mode by determining whether all film data belongs to 2:2 pull down or 3:2 pull down mode. For example, in the compression of an MPEG file, the order of the repeated image will be changed, so that the film mode will change to 4:3, 4:2, 3:3, 3:2, or 2:2 pull down when an MPEG file is played.
If the prior art techniques are used to detect the image of an MPEG file, instability of the film displaying will be caused by continuously entering or leaving movie mode. Moreover, if the operation of leaving film mode is not performed well, a sawtooth will be created whenever the video data is played, so that the quality of the image will be decreased.